X-Ray Diffraction Studies of the Lattice Parameters of Solids under Very High Pressure

TL;DR: In this article, the measurements of lattice parameters versus pressure made in this laboratory were discussed, primarily, the measurements were made by measuring the lattice parameter of a "marker" along with those of the substance studied.

Abstract: Publisher Summary This chapter discusses, primarily, the measurements of lattice parameters versus pressure made in this laboratory. The apparatus used permits a rather large range of pressure. (When studying a single cubic metal of low compressibility such as Ag, Nb, or Mo where one or two lines suffice, pressures of 550 kbar or more have, on occasion, been obtained. For substances where more lines are necessary, or for mixtures of substances, the range is more limited.) Some of the other methods of measurement permit more accuracy in the low-pressure region. There are no primary pressure standards in the very high pressure range. Pressures are established in this work by measuring the lattice parameter of a “marker” along with those of the substance studied. Commonly used markers include cubic metals such as Al, Ag, Nb, Mo, and Pd, where shock-wave densities corrected to room temperature have been shown to be internally consistent. Salts such as NaCl, MgO, NaF, and LiF that have been studied using these metallic markers have been utilized themselves to measure pressure. Markers are selected which have “windows” (spaces with no lines) in regions where the sample have prominent lines. Also, more compressible markers are used to establish more accurate pressures in the low-pressure region.